Rails 3.1 assets not resolving

Problem

I have a Rails 3.0.4 app which I upgrade to 3.1.4 following instructions from Railscast video: "Upgrading to rails 3.1".

Now I have problems with assets because they are not resolved, giving messages in server log like this:

Started GET "/assets/application.css" for 127.0.0.1 at 2012-04-08 03:57:13 -0500
Served asset /application.css - 404 Not Found (15ms)

ActionController::RoutingError (No route matches [GET] "/assets/application.css"):
Rendered /usr/local/rvm/gems/ruby-1.9.2-p318/gems/actionpack-3.1.4/lib/action_dispatch/middleware/templates/rescues/routing_error.erb within rescues/layout (14.3ms)

Started GET "/assets/application.js" for 127.0.0.1 at 2012-04-08 03:57:13 -0500
Served asset /application.js - 404 Not Found (35ms)

ActionController::RoutingError (No route matches [GET] "/assets/application.js"):

These files are in assets directory:

$ ls app/assets/*/application*
app/assets/javascripts/application.js   app/assets/stylesheets/application.css

and contains this:

$ cat app/assets/javascripts/application.js
//= require jquery
//= require jquery_ujs
//= require_self
//= require_tree .
$ cat app/assets/stylesheets/application.css
/*
*= require_self
*= require_tree .
*/

I suppose everything is configured. Here I put some chunks of files:

• Gemfile, contains assets gems required:

  group :assets do
    gem 'sass-rails', '~> 3.1.3'
    gem 'coffee-rails', '~> 3.1.0'
    gem 'uglifier'
  end
  

• application.rb, has assets enabled:

  config.assets.enabled = true
  config.assets.version = '1.0'
  

• development.rb:

  config.assets.compress = false
  config.assets.debug = t